This invention relates to a process and apparatus for modifying bitumen.
Modifying bitumen and more particularly modifying the properties of bitumen by oxidising the bitumen is known. Oxidised or so-called “blown bitumen” is obtained by blowing or passing air through the bitumen when the bitumen is at a very high temperature e.g. 200-350° C. typically 240 to 280° C. The resultant modified bitumen is harder i.e. has an increased softening temperature and viscosity at comparable temperatures.
With use of appropriate reagents the properties of the bitumen can be modified further such that the bitumen viscosity is less temperature susceptible. These multi-grade bitumens are also known in the art.
The process of modifying bitumen by blowing is relatively slow. It can also be inherently dangerous due to the presence of volatile hydrocarbons in any airspace within the bitumen modifying apparatus. The process may also result in significant carbon deposits. The process is frequently inefficient. There may also be present the real risk of fire or explosion and consequential damage to plant and potentially injury to personnel.
The traditional bitumen modifying process can be a batch or continuous process. According to a simple form of apparatus to carry out the process, bitumen at an elevated temperature can be loaded into a container and air introduced into the lower part of the container so as to pass up through the bitumen. For example, a sparge ring can be provided in the base of the container for injecting the air into the bitumen.
According to another method the air can be introduced through the top of a container in which bitumen is located. The air and bitumen is mixed by a rotating stirring element or elements located within the bitumen. In this way air becomes dispersed through the bitumen.